Lens barrel

ABSTRACT

A lens barrel according to the present invention includes a first lens group; a second lens group; a third lens group; a first actuator for driving the first lens group; a second actuator for driving the second lens group; and third and fourth actuators for driving the third lens group. At least one of the first through fourth actuators is provided at a position such that magnetic flux leakage from at least one of the first through fourth actuators is canceled.

TECHNICAL FIELD

The present invention relates to a lens barrel for use in a video cameraor the like.

BACKGROUND ART

Recently there is a demand for small-sized lens barrels for videocameras whose body-size is being reduced. Faster zooming or focusing isalso required.

Hereinafter, a conventional lens barrel will be described.

In general, a lens barrel for a video camera includes four lens groups.Movable lens groups of the four lens groups are moved in a direction ofan optical axis by guiding along a guide pole for the purposes ofzooming and focusing. The lens barrel includes a fixed lens group, alens group movable on the optical axis for zooming, another fixed lensgroup, a lens group movable on the optical axis for focusing, an irisunit, and an imaging plane. The zooming lens group and the focusing lensgroup are held by a zooming lens frame and a focusing lens frame,respectively. A zooming actuator and a focusing actuator for driving thezooming lens moving frame and the focusing lens frame in the opticalaxis direction, respectively, each include a stepping motor. The zoomingand focusing stepping motors each include a screw on the respectiveoutput axes. The zooming lens moving frame and the focusing lens frameare linked to each other by a linkage. Two guide poles are used to holdthe zooming lens moving frame and the focusing lens frame so that theframes can freely move in the optical axis direction. In such a lensbarrel, when a current is supplied to the zooming stepping motor via anelectrical signal line, the output axis is rotated so that the linkagewhich is engaged with the screw of the zooming stepping motor is movedin the optical axis direction. The zooming lens moving frame, i. e., thezooming lens group, which is engaged with the linkage, is then moved inthe optical axis direction. Similarly, when a current is supplied to thefocusing stepping motor via the electrical signal line, the output axisis rotated so that the linkage which is engaged with the screw of thefocusing stepping motor is moved in the optical axis direction. Thefocusing lens frame, i.e., the focusing lens group, which is engagedwith the linkage, is then moved in the optical axis direction.

Such a conventional structure has the following problems.

(1) The stepping motor used as the actuator in the conventional lensbarrel can be stopped at a predetermined position by rotating the motorby an angle corresponding to a predetermined number of pulses. However,since the driving control of the stepping motor is an open loop, thereare the following problems: the precision in the stopping positions ispoor; a hysteresis property exists; the number of revolutions isrelatively low, and the like. Therefore, when the stepping motor is usedas a driving power source of a transporting mechanism for the zooming orfocusing lens moving frame, the zooming or focusing speed is slow.Japanese Laid-Open Publication No. 8-266093 proposes a stepping motorsystem having an encoder as a solution to this above problem. As isdisclosed by the publication, a sensor is provided which detects therotational angle of a stepping motor. The sensor results in the controlsystem being a closed loop, thereby making it possible to achievehigh-speed driving. Japanese Laid-Open Publication No. 10-225083proposes a linear actuator system which can track the changing positionsof the focusing group using a voice type linear actuator. Such a linearactuator system has a high-speed response capability and lower powerconsumption.

Therefore, the lens driving system may be optimized by adopting astepping motor having an encoder for driving the zooming lens group; andby adopting a linear actuator for moving the focusing lens group, forthe purpose of the high-speed response capability and low powerconsumption. Such a system generally includes a magnetoresistance sensor(hereinafter referred to as a magnetic sensor) as a position detectionsensor in order to increase the precision of the position detection.

A small-sized and lightweight lens barrel is required for recentsmall-sized and lightweight video cameras. Therefore, intervals ofcomponents included in the lens barrel tend to be decreased. When aconventional magnetic sensor is affected by an external disturbancemagnetic field, the output of the sensor is distorted, causing a problemin that the performance of the actuator is deteriorated. Magnetic fluxleakage from a driving magnet occurs in the above-described steppingmotor having an encoder and linear actuator. Such magnetic flux leakageis not negligible in the case of a small-sized lens barrel since thegaps between the parts thereof are narrow. In particular, the drivingmagnet of the linear actuator has an adverse influence on the magneticsensor of the stepping motor having an encoder. Conventionally, anadditional part such as a magnetic shield has been used to address themagnetic flux leakage problem. However, such a magnetic shield leads toan increase in cost. The provision of a space for the magnetic shieldhinders achievement of the small-sized lens barrel. Therefore, a systemincluding the small-sized and lightweight lens barrel, the steppingmotor having an encoder, and the linear actuator cannot realize thehigh-speed response capability and low power consumption in driving thezooming and focusing lenses.

(2) A small-size, lightweight and high-magnification lens barrel poses aproblem that hand-shake makes it difficult to obtain a stable image atthe furthermost focusing point. A conventional solution to the problemis an electric hand-shake compensation system. The compensation extentneeds to be expanded with an increase in the degree of hand-shake in thesmaller-sized, lighter-weight, and higher magnification lens barrel. Thecompensation extent to the hand-shake in the electrical compensationsystem depends on the number of pixels in the CCD, requiring manypixels. Smaller-sized CCDs and higher picture quality video cameras poselimitations to the increased number of pixels allowed in the CCD,whereby the electric hand-shake compensation system does not workeffectively.

Optical hand-shake compensation systems have been proposed whosecompensation extents are large and in which high picture quality isobtained. As one of the optical hand-shake compensation systems,Japanese Laid-Open Publication No. 3-186823 discloses a so-calledinner-shift system in which the hand-shake is compensated by moving apredetermined lens group (shift lens group) in a direction perpendicularto the optical axis. In the inner shift system, a lens group requiredfor focusing is also used as the shift lens group for compensating thehand-shake. Therefore, a short, small-sized, and lightweight lens barrelcan be realized.

However, two additional actuators are required for moving thecompensation lens group in a direction perpendicular to the opticalaxis. In addition to the actuators for zooming, focusing, and the irisincluded in the conventional lens barrel, two shift actuators arerequired for compensating the hand-shake. That is, five actuators needto be provided in a single lens barrel. This increased number ofactuators makes it difficult to obtain a small-sized lens barrel, whichruns against the recent tide of small-sized lens barrels. In this case,it is important to arrange these actuators in a compact manner.

(3) As indicated in problem (1), when the stepping motor having anencoder using the magnetic sensor, and the linear actuator are used asthe zooming and focusing actuators, respectively, magnetic flux leakagefrom the two shift actuators for image shake compensation occurs,adversely affecting the magnetic sensor.

Therefore, an object of the present invention is to provide a lensbarrel which can eliminate the adverse effect of the magnetic fluxleakage occurring in the actuator on the magnetic sensor.

DISCLOSURE OF THE INVENTION

A lens barrel according to the present invention includes a first lensgroup; a second lens group; a third lens group; a first actuator fordriving the first lens group; a second actuator for driving the secondlens group; and third and fourth actuators for driving the third lensgroup. At least one of the first through fourth actuators is provided ata position such that magnetic flux leakage from at least one of thefirst through fourth actuators is canceled. Thereby, the above object isachieved.

The first actuator may include a stepping motor; a first magnet in theshape of a barrel or column, magnetized to have multiple poles in acircular direction, and attached coaxially to the stepping motor in sucha manner as to rotate; and a first magnetic sensor provided opposing anouter edge of the first magnet. The second actuator includes a secondmagnet magnetized perpendicular to a driving direction; a yoke; a coilprovided at a predetermined gap from the second magnet, capable offreely moving in the driving direction when a current is suppliedthereto in such a manner as to flow in a direction perpendicular tomagnetic flux generated by the second magnet; and a second magneticsensor. The first magnetic sensor may be provided at a position suchthat magnetic flux leakage from a magnetic circuit including the secondmagnet and the yoke is canceled.

The second actuator may include a magnet magnetized perpendicular to adriving direction; a yoke; a coil provided at a predetermined gap fromthe magnet, capable of freely moving in the driving direction when acurrent is supplied thereto in such a manner as to flow in a directionperpendicular to flux generated by the magnet; and a magnetic sensor.The magnetic sensor may be provided at a position such that magneticflux leakage from at least one of the third and fourth acturator iscanceled.

The third actuator may include a third magnet, the fourth actuatorincludes a fourth magnet; and the third magnet and the fourth magnet areprovided in such a manner that the magnetization of the third and fourthmagnets is reversed when viewed in the center of an optical axis.

The first actuator may include a stepping motor; a first magnet in theshape of a barrel or column, magnetized to have multiple poles in acircular direction, and attached coaxially to the stepping motor in sucha manner as to rotate; and a magnetic sensor provided opposing an outeredge of the first magnet. The third and fourth magnets may be providedat positions such that magnetic flux leakage to the magnetic sensor iscanceled.

The lens barrel may further include first and second lens moving framesholding the third lens group and capable of being smoothly moved infirst and second directions perpendicular to an optical axis,respectively. One of the third or fourth actuators provided at anoptical axis imaging plane side may be provided overlapping the lensmoving frame provided at an optical axis object side when viewed in theoptical axis direction.

The second actuator may be provided at an optical axis imaging planeside of one of the third and fourth actuators provided at an opticalaxis object side, overlapping one of the third and fourth actuators,when viewed in the optical axis direction.

The lens barrel may further include first and second lens moving framesholding the third lens group and capable of being smoothly moved infirst and second directions perpendicular to the optical axis,respectively; and a fixing frame holding the first and second lensmoving frames, leaving the first and second lens moving frames capableof being smoothly moved. The fixing frame may include a depression in aportion surrounded by the third and fourth actuators; and the firstactuator is provided in the depression.

The lens barrel may further include an actuator for driving an iris. Theactuator for driving the iris may be provided at the optical axis objectside of one of the third and fourth actuators provided at an opticalaxis imaging plane side.

The lens barrel may further include first and second lens moving framesholding the third lens group, provided at different heights with respectto an optical axis, and capable of being smoothly moved in first andsecond directions perpendicular to the optical axis; a first lightemitting portion incorporated into the first lens moving frame fordetecting a position of the first lens moving frame; and a second lightemitting portion incorporated into the second lens moving frame fordetecting a position of the second lens moving frame. The first andsecond light emitting portions may be provided at substantially the sameheight when viewed in the optical axis direction.

The lens barrel may further include first and second lens moving framesholding the third lens group, and capable of being smoothly moved infirst and second directions perpendicular to an optical axis; and afixing frame fixing the first and second lens moving frames, leaving thefirst and second lens moving frames capable of being smoothly moved. Thethird actuator may drive the first lens moving frame. The fourthactuator may drive the second lens moving frame. The lens barrel mayfurther include a first flexible print cable electrically connected tothe third actuator; and a second flexible print cable electricallyconnected to the fourth actuator. One end of the first flexible printcable may be fixed to the first lens moving frame at a side thereofopposite to the third actuator with respect to the optical axis and atthe same side as that of the fourth actuator. One end of the secondflexible print cable may be fixed to the second lens moving frame at aside thereof opposite to the third and fourth actuators with respect tothe optical axis. Other ends of the first and second flexible printcables may be fixed to the fixing frame at a side thereof opposite tothe fourth actuator with respect to the optical axis, beingsubstantially parallel to a direction along which the first lens movingframe is smoothly moved.

The first flexible print cable may be provided at an outside from thecenter of the optical axis with respect to the second flexible printcable.

The first and second flexible print cables may be provided at differentheights with respect to the optical axis of the third lens group.

Moving portions of the first and second flexible print cables and anoutline of the fixing frame corresponding to the moving portions of thefirst and second flexible print cables may be substantially in the shapeof a circular arc. The moving portions of the first and second flexibleprint cables may move along the fixing frame.

Another lens barrel according to the present invention includes a firstlens group; a second lens group; a third lens group; a first actuatorfor driving the first lens group; a second actuator for driving thesecond lens group; third and fourth actuators for driving the third lensgroup; first and second lens moving frames holding the third lens groupand capable of being smoothly moved in first and second directionsperpendicular to an optical axis; and a fixing frame fixing the firstand second lens moving frames, leaving the first and second lens movingframes capable of being smoothly moved. The third actuator drives thefirst lens moving frame. The fourth actuator drives the second lensmoving frame. The lens barrel further includes: a first flexible printcable electrically connected to the third actuator. A second flexibleprint cable electrically connected to the fourth actuator. One end ofthe first flexible print cable is fixed to the first lens moving frameat a side thereof opposite to the third actuator with respect to theoptical axis and at the same side as that of the fourth actuator. Oneend of the second flexible print cable is fixed to the second lensmoving frame at a side thereof opposite to the third and fourthactuators with respect to the optical axis. Other ends of the first andsecond flexible print cables are fixed to the fixing frame at a sidethereof opposite to the fourth actuator with respect to the opticalaxis, being substantially parallel to a direction along which the firstlens moving frame is smoothly moved. Thereby, the above-described objectis achieved.

The first flexible print cable may be provided at an outside from thecenter of the optical axis with respect to the second flexible printcable.

The first and second flexible print cables may be provided at differentheights with respect to the optical axis of the third lens group.

Moving portions of the first and second flexible print cables and anoutline of the fixing frame corresponding to the moving portions of thefirst and second flexible print cables may be substantially in the shapeof a circular arc. The moving portions of the first and second flexibleprint cables may move along the fixing frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are a rough perspective view of a lens barrelincluding a linear actuator and a stepping motor having an encoderaccording to Example 1 of the present invention, with FIG. 1(a) beingthe front view and FIG. 1(b) being the reverse view.

FIGS. 2(a) and 2(b) are a conceptual diagram showing a flow of magneticflux leakage from the linear actuator according to Example 1 of thepresent invention, with FIG. 2(a) being a side view and FIG. 2(b) beinga top view.

FIG. 3 is a diagram showing the magnetoresistance change characteristicsof an MR element.

FIG. 4 is a rough perspective view of a position detection portionincluding an MR element.

FIGS. 5(a) and 5(b) are a conceptual diagram showing a flow of magneticflux leakage to the stepping motor having an encoder according toExample 1 of the present invention, with FIG. 5(a) being a top view andFIG. 5(b) being a side view.

FIGS. 6(a) and 6(b) are a conceptual diagram showing a flow of magneticflux leakage to a magnetic sensor according to Example 1 of the presentinvention, with FIG. 6(a) being a top view and 6(b) being a side view.

FIG. 7 is a rough perspective view of a lens barrel including an imageshake compensation device and a linear actuator according to Example 2of the present invention.

FIG. 8 is a perspective view of key parts of the is image shakecompensation device according to Example 2 of the present invention.

FIG. 9 is a block diagram of the image shake compensation deviceaccording to Example 2 of the present invention.

FIG. 10 is a rough perspective view of a lens barrel including an imageshake compensation device and a linear actuator according to Example 3of the present invention.

FIG. 11 is a diagram showing an arrangement of a yoke of an actuatoraccording to Example 3 of the present invention.

FIG. 12 is a diagram showing a flow of magnetic flux of a magnet of ashift actuator for the image shake compensation device according toExample 3 of the present invention.

FIGS. 13(a) and 13(b) are diagrams showing a flow of magnetic flux of amagnet of a linear actuator according to Example 3 of the presentinvention, with FIG. 13(a) being a top view and FIG. 13(b) being a sideview.

FIG. 14 is a rough perspective view of a lens barrel including an imageshake compensation device and a stepping motor having an encoderaccording to Example 4 of the present invention.

FIG. 15 is a front view of the lens barrel according to Example 4 of thepresent invention.

FIGS. 16(a) and 16(b) are diagrams showing a flow of magnetic flux of animage shake compensation device according to Example 5 of the presentinvention, with FIG. 16(a) showing the flow yawing and FIG. 16(b)showing the flow pitching.

FIGS. 17(a) and 17(b) are diagrams of the lens barrel according toExample 5 of the present invention to which a linear actuator is added,with FIG. 17(a) showing the front view and FIG. 17(b) showing theopposite view.

FIG. 18 is a rough perspective view of a lens barrel including an imageshake compensation device, a stepping motor having an encoder, and aniris unit according to Example 6 of the present invention.

FIG. 19 is a front view of the lens barrel according to Example 6 of thepresent invention.

FIG. 20 is a perspective view of the lens barrel according to Example 6of the present invention.

FIG. 21 is a diagram showing the PSD substrate of a lens barrelaccording to Example 7 of the present invention.

FIG. 22 is a diagram showing the arrangement of an LED and a PSD of thelens barrel according to Example 7 of the present invention.

FIG. 23 is a front view of yawing of an image compensation device of alens barrel according to Example 8 of the present invention.

FIG. 24 is a front view of pitching of the image compensation device ofthe lens barrel according to Example 8 of the present invention.

FIG. 25 is a front view of an image compensation device of a lens barrelaccording to Example 9 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Example 1

Hereinafter, a lens barrel according to Example 1 of the presentinvention will be described with reference to FIGS. 1 through 6. FIG. 1is a rough perspective view of the lens barrel including a linearactuator and a stepping motor having an encoder according to Example 1of the present invention. FIG. 2 is a conceptual diagram showing a flowof magnetic flux leakage from the linear actuator. FIG. 3 is a diagramshowing the magnetoresistance change characteristics of an MR element.FIG. 4 is a rough perspective view of a position detection portionincluding the MR element. FIG. 5 is a conceptual diagram showing a flowof magnetic flux leakage to the stepping motor having an encoder. FIG. 6is a conceptual diagram showing a flow of magnetic flux leakage to amagnetic sensor according to Example 1 of the present invention.

A focusing lens moving frame 31 holds a focusing lens group 30, beingdirected in parallel to an optical axis thereof. The focusing lensmoving frame 31 is smoothly moved along guide poles 32 a and 32 b, whoseends (not shown) are fixed to the lens barrel, in an optical axisdirection (X-direction). A fixing member 34 of a linear actuator 33 isprovided in the lens barrel for driving the focusing lens moving frame31 in the optical axis direction. The fixing member 34 includes a mainmagnet 35 having a magnetization direction perpendicular to the drivingdirection (X-direction), a U-shaped main yoke 36, and a plate-shapedside yoke 37.

A magnetic circuit 38 including the fixing member 34 is laterallysymmetrical when viewed in the driving direction and is substantiallylaterally symmetrical when viewed in the driving direction (Xdirection). A moving member 39 of the actuator 33 includes a coil 40which is fixed to the focusing lens moving frame 31 in such a manner tocreate a predetermined gap between the coil 40 and the magnet 35. Acurrent is supplied to the coil 40, flowing in a direction perpendicularto that of the magnetic flux generated by the magnet 35. Thereby, thefocusing lens moving frame 31 is driven in the optical axis direction.

In order to control the position of the focusing lens moving frame 31, amagnetic sensor 41 is provided as a position detection device in thelens barrel on the fixed side at the center position around which themagnetic circuit 38 is symmetrical when viewed in the driving direction(X direction) and at the center position around which the magneticcircuit 38 is symmetrical when viewed in the driving direction. Amagnetic scale 42 including alternating N poles and S poles is attachedto the focusing lens moving frame 31 at a predetermined distance awayfrom the detection surface of the magnetic sensor 41 opposed thereto.The magnetic sensor 41 is a two-phase magnetoresistance sensor includingMR elements 43 a and 43 b made of a ferromagnetic thin film. The MRelements 43 a and 43 b are provided in the driving direction atintervals of a ¼ of the pitch between the N pole and the S pole. Themagnetic sensor 41 and the magnetic scale 42 are provided so that thedirection of a current flowing through the MR elements 43 a and 43 b isperpendicular to the magnetization direction of the magnet 35.

Next, a position detection method using the magnetic sensor 41 will bedescribed. As to the directional property of the magnetoresistancechange shown in FIG. 3, the resistance is substantially independent of amagnetic field in a direction (Y direction) perpendicular to the currentdirection of the MR elements 43 a and 43 b and perpendicular to thedetection surface; the resistance greatly changes depending on amagnetic field in a direction (X direction) perpendicular to the currentdirection of the MR elements 43 a and 43 b and parallel to the detectionsurface; and the resistance slightly changes depending on a magneticfield in a direction (Z direction) parallel to the current direction ofthe MR elements 43 a and 43 b.

Due to such characteristics, when the position of the magnetic scale 42having a magnetization pattern as shown in FIG. 4 is changed withrespect to the magnetic sensor 41, the resistances of the MR elements 43a and 43 b change in accordance with a sine-wave pattern of magneticfield variation occurring along the X direction. Although a sine-wavepattern of magnetic field variation whose phase is different from thatin the X direction by 180° also occurs in the Y direction, theresistances of the MR elements 43 a and 43 b do not substantially changedue to the abovedescribed characteristics. Therefore, when a voltageapplied to the MR elements 43 a and 43 b is used as an output signal,the output signal has the two sine waves whose phases are different fromeach other by 90°. The two signal waves are subjected to a modulationinterpolation processing by a signal processing circuit (not shown),thereby detecting the position and driving direction of the lens movingframe 31. Based on these data, the position of the focusing lens group30 can be controlled with a high precision by a control circuit (notshown).

However, in order to realize a high-precision linear actuator, anexternal disturbance magnetic field entering the magnetic sensor 41needs to be suppressed. When an external disturbance magnetic field ispresent in the optical axis direction (X direction) in the linearactuator 33, the external disturbance magnetic field is superposed onthe sine-wave pattern of magnetic field intensity variation. Therefore,a signal wave is offset, so that the waveform of the output signal isdistorted. This leads to an increase in an error in the positiondetection. Although the sensitivity to the magnetoresistance change issmall in a direction (Z direction) orthogonal to the optical axis, thechange rate of the magnetoresistance is decreased and therefore thesensitivity of the MR elements is deteriorated.

Therefore, the linear actuator 33 needs to avoid the influence of theexternal disturbance magnetic field, particularly by the influence ofthe main magnet 35, with respect to the X and Z directions.

As described above, the magnetic flux leakage is reduced by providingthe magnetic sensor 41 at the center of the magnetic circuit 38. Asshown in FIG. 2(a), the MR elements 43 a and 43 b have a property inwhich the magnetoresistance changes in the X and Z directions. Since themagnetic circuit 38 is substantially symmetrical with respect to thedriving direction (X direction), the amount of magnetic flux leakage isvery small in the X direction of the magnetic sensor 41 positioned atthe center of the symmetry. Also, as shown in FIG. 2(b),sincethemagnetic circuit 38 is substantially symmetrical with respect tothe driving direction, the amount of magnetic flux leakage is very smallin the Z direction of the magnetic sensor 41 positioned at the center ofthe symmetry. As described above, the optimization of the position ofthe magnetic sensor 41 leads to a reduction in magnetic flux leakage.

A stepping motor 47 having an encoder for moving a zooming lens group 45in the optical axis direction will be described.

The stepping motor 47 having an encoder includes a stepping motor 48, alead screw 49 which is combined with the rotational axis of the steppingmotor, a sensor magnet 50 having alternating N poles and S poles, and afixed magnetic sensor 51 for detecting angles opposed to the sensormagnet 50. Note that in FIG. 1, the sensor magnet 50 and the magneticsensor 51 are covered with a cover 51 a for fixing the magnetic sensor51. For the lead screw 49, a zooming lens moving frame 46 holding thezooming lens group 45 is coupled with a screw member 52 which is engagedwith the lead screw 49.

Therefore, the zooming lens group 45 is linearly moved in the X-axisdirection by rotation of the lead screw 49. A CPU (not shown) of asystem for the stepping motor having an encoder evaluates information onthe angle of the rotational axis and information on an electrical phaseangle based on a counted value from a counter for the electrical phase.The CPU evaluates a drive instruction value based on the angleinformation and the electrical phase angle information. The steppingmotor 47 having an encoder is controlled by flowing a driving current bya driver.

However, when the magnetic sensor 51 of the stepping motor 47 having anencoder is affected by the external disturbance magnetic field, theoutput of the magnetic sensor 51 is distorted, similar to the magneticsensor 41 of the linear actuator 33. The performance of the actuator isdeteriorated. Note that the limit of the magnitude of the externaldisturbance magnetic field is about 10 gauss for the magnetic sensor 41of the liner actuator 33. The magnetic sensor 51 of the stepping motor47 having an encoder has a smaller limit compared with the limit of theexternal disturbance magnetic field for the linear actuator 33, in partbecause the sensor magnet 50 is barrel-shaped and the magnetic sensorsurface is flat.

The stepping motor 47 having an encoder has less influence on theexternal disturbance magnetic field from the magnet 48 a of the steppingmotor 48. Nevertheless, since the lens barrel is small sized, thedistance between the stepping motor 47 and the linear actuator 33 issmall. In particular, the stepping motor 47 is likely to be affected bythe main magnet 35 of the linear actuator 33. Accordingly, in thestepping motor 47 having an encoder, the magnetic sensor 51 needs to beprovided at a position at which the magnetic sensor 51 is unlikely to beaffected by the external disturbance magnetic field. This condition willbe described.

When the magnetic sensor 51 is provided at a position indicated in FIGS.5 and 6 in the stepping motor 47 having an encoder, the externaldisturbance magnetic field needs to be suppressed in two directions,i.e., the tangential direction (Z direction) of the rotational directionof the sensor magnet 50 and in the current direction (X direction) inthe magnetic sensor 51. The magnetic sensor 51 of the stepping motor 47having an encoder is provided based on the following principle. Sincethe magnetic circuit 38 of the linear actuator 33 is laterallysymmetrical when viewed in the driving direction, the magnetic sensor 51positioned at the center of the symmetry detects substantially nomagnetic flux leakage in the Z direction. Similarly, since the magneticcircuit 38 is substantially symmetrical when viewed in the X direction,the magnetic sensor 51 positioned at the center of the symmetry detectssubstantially no magnetic flux leakage in the X direction. Therefore,the magnetic sensor 51 of the stepping motor 47 having an encoder is notinfluenced by the external disturbance magnetic field, thereby realizinga high-precision actuator system.

As described above, according to Example 1, a system can be providedwhich includes the stepping motor having an encoder for zooming and thelinear actuator for focusing, instead of a system using a conventionalstepping motor. Therefore, the zooming function can have a transportingspeed of about 30-2000 pps. Hyper-high-speed or hyper-slow-speed zoomingcan be performed. A high-performance lens barrel and a video camerausing the same can be provided.

Further, when the closed loop control is used, the angle of rotation andtorque can be controlled, thereby realizing low power consumption andlow noise. As to focusing, high resolution and high precision can beobtained in addition to a high response capability by use of themagnetic sensor, thereby realizing excellent focusing characteristics.Furthermore, the external disturbance magnetic field can only be reducedby the arrangement of the magnetic sensor described above. Thus, a partsuch as a shield is not used, in contrast to the conventional method,thereby achieving low cost and preventing the size of the lens barrelfrom being increased with an increase in space for such parts. Asmall-sized and lightweight lens barrle can therefore be provided.

Needless to say, the same effects can be obtained even when the polarityof the main magnet of the linear actuator of Example 1 as shown in FIGS.2, 5, and 6 is reversed.

In the linear actuator of Example 1, the magnetic sensor is provided onthe lens barrel at the fixed side and the magnetic scale is provided onthe lens moving frame at the moving side. Alternatively, the magneticscale is provided on the lens barrel at the fixed side and the magneticsensor is provided on the lens moving frame at the moving side. In thiscase, it is needless to say that the same effects can be obtained.

Although a magnetoresistance type magnetic sensor including the MRelement is used in Example 1, a magnetic sensor of any type can be usedso long as it puts out an output signal corresponding to the intensityof magnetic force.

Example 2

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 7 through 9. FIG. 7 is a rough perspective viewof a lens barrel including an image shake compensation device and alinear actuator according to Example 2 of the present invention. FIG. 8is a perspective view of key parts of the image shake compensationdevice. FIG. 9 is a block diagram of an image shake compensationcircuit. The parts described above are indicated by the same referencenumerals and their descriptions are omitted.

A first lens group for compensating image shake when taking a picture isfixed on a holding frame 2 capable of moving in the Z direction as shownin FIG. 7. Hereinafter, the holding frame 2 is referred to as a pitchingmoving frame 2. The pitching moving frame 2 can be moved smoothly viatwo pitching shafts 3 a and 3 b by providing a bearing 2 a and a detent2 b on a side opposite to the bearing 2 a. An electromagnetic actuator 6p is also provided under the pitching moving frame 2.

The electromagnetic actuator 6 p includes a coil 7 p attached to thepitching moving frame 2, a magnet 8 p, and a yoke 9 p attached to afixing frame 10 described later. Protrusions 9 pa are provided onopposite sides of the yoke 9 p. Engagement holes 10 pa capable ofengaging with the protrusions 9 pa are provided in the fixing frame 10,laying in a direction substantially parallel to a direction along whichthe pitching moving frame 2 is smoothly moved. Therefore, the yoke 9 pis fixed to the fixing frame 10 without adhesion or the like. Two polemagnetization is provided in one surface of the magnet 8 p which isfixed to the U-shaped yoke 9 p, one side of which is open.

A frame 4 for moving the image shake compensation lens group 1 in the Ydirection is attached to the pitching moving frame 2 at the optical axisimaging plane side thereof. Hereinafter, the holding frame 4 is referredto as a yawing moving frame. Fixing members 4 c and 4 d are provided inthe yawing moving frame 4 at the optical axis object side for fixing theopposite ends of the two pitching shafts 3 a and 3 b which are used forsmoothly moving the pitching moving frame 2 as described above.Similarly, the yawing moving frame 4 is moved smoothly via two yawingshafts 5 a and 5 b by providing a bearing 4 a and a detent 4 b on a sideopposite to the bearing 4a. The two yawing shafts 5 a and 5 b are fixedto fixing portions 10 c and 10 d of the fixing frame 10 provided at theoptical axis imaging plane side of the yawing moving frame 4. Anelectromagnetic actuator 6 y is provided at the left side of the yawingmoving frame 4.

The electromagnetic actuator 6 y includes a coil 7 y attached to theyawing moving frame 4, a magnet 8 y, and a yoke 9 y attached to thefixing frame 10. Protrusions 9 ya are provided on opposite sides of theyoke 9 y. Engagement holes 10 ya capable of engaging with theprotrusions 9 ya are provided in the fixing frame 10, laying in adirection substantially parallel to a direction along which the yawingmoving frame 4 is smoothly moved. Therefore, the yoke 9 y is fixed tothe fixing frame 10 without adhesion or the like. Two pole magnetizationis provided in one surface of the magnet By which is fixed to theU-shaped yoke 9 p one side of which is open.

Therefore, when a current flows through the coil 7 p of the pitchingmoving frame 2, electromagnetic force is generated in the Z direction bythe magnet 8 p and the yoke 9 p. Similarly, when a current flows throughthe coil 7 y of the yawing moving frame 4, electromagnetic force isgenerated in the Y direction by the magnet By and the yoke 9 y. In thisway, the image shake compensation lens group 1 is driven in the twodirections substantially perpendicular to the optical axis by the twoelectromagnetic actuators 6 p and 6 y.

Next, the position detection portion will be described. A detectionportion 11 p provided at the upper portion in the Z direction of thepitching moving frame 2 includes a light emitting element 12 p (such asLEDs), a slit 13 p, and a light receiving element 14 p (PSD) attached toa PSD substrate 15. Similarly, a detection portion 11 y provided at theupper portion in the Y direction of the pitching moving frame 4 includesa light emitting element 12 y (such as LEDs), a slit 13 y, and a lightreceiving element 14 y (PSD) attached to the PSD substrate 15.

The light emitting elements 12 p and 12y emit light beams through therespective slits 13 p and 13 y. The light beams which have passedthrough the slits 13 p and 13 y enter the respective light receivingelements 14 p and 14 y. Therefore, the movement of the image shakecompensation lens group 1 is equivalent to the movement of the lightreceiving elements 14 p and 14 y. The light receiving elements 14 p and14 y output information on the positions of: the light beams incident tolight receiving surfaces thereof as two current values. The outputvalues are calculated to detect the position of the lens group 1.

Next, a flexible print cable connected between the pitching and yawingmoving frames 2 and 4 and the fixing frame 10 will be described.

A flexible print cable 16 is attached onto an upper surface of thepitching moving frame 2 in such a manner as to surround the compensationlens group 1. The flexible print cable 16 is electrically connectedbetween the coil 8 p and the light emitting element 12 p. The flexibleprint cable 16 is fixed at a portion 16 b thereof to the pitching movingframe 2, being oriented perpendicular to the smooth moving direction Z.The other end 16a of the flexible print cable 16 is fixed to a portion10 e of a side of the fixing frame 10, the end 16 a being parallel tothe smooth moving Z direction of the pitching moving frame 2.

Therefore, the coil 7 p and the light emitting element 12 p areconnected to a circuit (not shown) for supplying a driving current.Similarly, a flexible print cable 17 is attached onto a side of theyawing moving frame 4. The flexible print cable 17 is electricallyconnected between the coil 7 y and the light emitting element 12 y. Theflexible print cable 17 is fixed at a portion 17 b thereof to the yawingmoving frame 4, the flexible print cable 17 being oriented parallel tothe smooth moving direction Y. The other end 17 a of the flexible printcable 17 is fixed to the portion 10 e on the side of the fixing frame10, the other end 17 a being substantially parallel to the smooth movingdirection Z of the pitching moving frame 2. Therefore, the coil 7 y andthe light emitting element 12 y are connected to a circuit (not shown)for supplying a driving current. Thus, the shift unit 20 for image shakecompensation includes the above-described parts.

Further, the shift unit 20 has a structure as shown in FIG. 8illustrating an assembly of the shift unit such that the dimensionsthereof in the lens diameter direction are reduced. The pitching movingframe 2 and the yawing moving frame 4 have different heights in theoptical axis direction. The pitching moving frame 2 is provided at theoptical axis object side. The yoke 9 y of the shift actuator 6 y foryawing is inserted into the optical axis imaging plane side of thebearing 2 a of the pitching moving frame 2 in such a manner that theyoke 9 y overlaps the bearing 2 a when viewed in the optical axisdirection. Therefore, a dimension in the radius direction of the shiftunit 20, i.e., a width B, can be reduced, leading to a downsizing of theshift unit 20.

The operation of the lens barrel thus constructed will be described.

A hand movement acting on a video camera including the image shakecompensation device is detected by two angular velocity sensors 21 (notshown) provided about 90° apart from each other. The outputs of theangular velocity sensors 21 are integrated with respect to time. Theresulting value is converted to an angle of hand-shake. The resultingangle is then converted to target position information of the imageshake compensation lens group 1. A servo circuit 22 calculates adifference between information on the target position and information onthe present position of the image shake compensation lens group 1, inorder to move the image shake compensation lens group 1 in accordancewith the target driving position information. The resulting differenceis transferred as a signal to the electromagnetic actuators 6 p and 6 y.The electromagnetic actuators 6 p and 6 y drive the image shakecompensation lens group 1 based on the signal. The movement of the imageshake compensation lens group 1 is detected by the position detectionportions 11 p and 11 y, and is fed back to compensate the image shake inthe video camera.

The yawing moving frame 4 is driven in the Y direction in the followingway. A current is supplied via the flexible print cable 17 to the coil 7y in response to an instruction from the driving circuit. The flow ofthe current causes the electromagnetic actuator 6 y to generate force inthe Y direction which drives the yawing moving frame 4. The pitchingmoving frame 2 is driven in the Z direction in the following way. Acurrent is supplied via the flexible print cable 16 to the coil 7 p inresponse to an instruction from the driving circuit. The flow of thecurrent causes the electromagnetic actuator 6 p to generate force in theZ direction which drives the pitching moving frame 2. Therefore, thecompensation lens group 1 can be arbitrarily moved in a planeperpendicular to the optical axis, thereby making it possible tocompensate image shake generated by hand movement.

As described above, according to Example 1, the pitching and yawingmoving frames for moving the compensation lens group in directionsperpendicular to the optical axis are provided in the lens barrelincluding the shift unit for compensating image shake. The pitching andyawing moving frames are positioned at different heights with respect tothe optical axis. The actuator of the yawing moving frame is provided insuch a manner as to overlap the pitching moving frame when viewed in theoptical axis direction. Therefore, the dimensions of the shift unit inthe width direction thereof can be reduced, thereby realizing adownsizing of the lens barrel including the shift unit.

Example 3

Next, a third embodiment of the present invention will be described withreference to FIGS. 10 through 13. FIG. 10 is a rough perspective view ofa lens barrel including an image shake compensation device and a linearactuator according to Example 3 of the present invention. FIG. 11 is adiagram showing an arrangement of a yoke of the linear actuator. FIG. 12is a diagram showing a flow of magnetic flux of a shift actuator for theimage shake compensation device. FIG. 13 is a diagram showing a flow ofmagnetic flux of a magnet of the linear actuator according to Example 3of the present invention. The parts described above are indicated by thesame reference numerals and their descriptions are omitted.

A shift unit 20 of Example 3 is identical to that described in Example2. For the sake of. simplicity, a fixing frame 10 of the shift unit 20is omitted from FIG. 11. The direction of magnetization of a pitchingmagnet 8 p, a yawing magnet 8 y and a magnet 35 of a linear actuator 33is as shown in FIGS. 12 and 13(a). A pitching moving frame 2 and theyawing moving frame 4 are positioned at different heights with respectto the optical axis direction. The pitching moving frame 2 is providedon the optical axis object side.

A main yoke 36 and a side yoke 37 of the linear actuator 33 for drivinga focusing lens group 30 as described in Example 1 are provided on theoptical imaging plane side of a yoke 9 p included in a pitching actuator6 p. A top view of the arrangement of the actuators of the shift unit 20and the linear actuator 33 is provided in FIG. 11. A magnetic sensor 41is used as a position detection portion of the linear actuator 33. Aspreviously described, an influence of an external disturbance magneticfield causes distortion of the sensor output, leading to deteriorationin performance of the actuators.

Therefore, in order to provide the shift unit 20 and the linear actuator33 in a single lens barrel, magnetic flux leakage from the shift unit 20and the linear actuator 33 needs to be reduced. Although a solution toprovide such a reduction in magnetic flux leakage is to enlarge the gapbetween the shift unit 20 and the linear actuator 33, this leads to anupsizing of the lens barrel. Therefore, in order to achieve a downsizingin the optical axis direction, the magnetic flux leakage needs to bereduced while keeping a small gap between the shift unit 20 and thelinear actuator 33. A reduction method will be described.

The magnetic sensor 41 of the linear actuator 33 is provided at thecenter position of a magnetic circuit 38 with respect to two directions,i.e., the optical axis direction (X direction) and a directionperpendicular thereto (Z direction), where an influence of an externaldisturbance magnetic field is substantially zero, thereby reducing themagnetic flux leakage. In this situation, when the magnetization of themagnet 8 p of the pitching actuator 6 p is as shown in FIG. 10, such aposition of the magnetic sensor 41 leads to the occurrence of themagnetic flux leakage as shown in FIG. 12 due to an influence of thepitching actuator 6 p. The position of the magnetic sensor 41 describedin Example 1 is a position in the Z axis direction indicated by thewhite circle.

Since magnetic flux leakage exists in the −Z direction due to theinfluence of the pitching actuator 6 p, the magnetic flux leakage entersthe magnetic sensor 41 at the position indicated by the white circle.When the magnetization of the main magnet 35 of the linear actuator 33is as shown in FIG. 10, magnetic flux leakage occurs as indicated by thewhite circle. Therefore, the magnetic sensor 41 is shifted by distance bin the Z direction to a position indicated by the black circle. As aresult, the magnetic flux leakage from the pitching actuator 6 p towardthe Z axis direction and the magnetic flux leakage from the linearactuator 33 toward the Z axis direction cancel each other out, wherebythe amount of the magnetic flux leakage which enters the magnetic sensor41 is substantially zero.

The pitching actuator 6 p has no influence on the magnetic sensor 41with respect to the X direction. Moreover, since the position in the Xdirection of the magnetic sensor 41 is not changed, the magnetic sensor41 is positioned at the magnetic center in the X direction of themagnetic circuit 38 of the linear actuator 33. Therefore, the linearactuator has no influence on the magnetic sensor 41. Note that theinfluence of the magnetic flux leakage from the yawing actuator 6 y issmall compared to the pitching actuator 6 p because of the long distancefrom the yawing actuator 6 y.

As described above, according to Example 3, the linear actuator can beprovided in the lens barrel including the shift unit for compensatinghand-shake, since the linear actuator is positioned so that the linearactuator is not influenced by an external disturbance magnetic field.Therefore, the focusing lens group is driven by the linear actuator, sothat a high-speed response capability is achieved. In addition, highresolution and high precision can be obtained using the magnetic sensor,thereby realizing an excellent focusing property.

Further, the reduction of magnetic flux leakage is achieved only bydevising the position of the magnetic sensor provided, in contrast tothe conventional technique. Apart such as a shield is not required,thereby achieving low cost and preventing the size of the lens barrelfrom being increased with an increase in space for parts.

Further, the pitching and yawing moving frames of the shift unit areprovided at different heights in the optical axis direction. The linearactuator for driving a focusing lens is provided immediately at theoptical axis imaging plane side of the pitching actuator provided at theoptical axis object side. Therefore, the dimension in the widthdirection can be shortened while a space in the optical axis directionis effectively used, thereby realizing a downsizing of the lens barrel.

Needless to say, the same effects can be obtained in Example 3 even ifthe polarity of the magnets of the pitching actuator and the linearactuator of the shift unit as shown in FIG. 10 is reversed.

Example 4

Next, a fourth embodiment of the present invention will be describedwith reference to FIGS. 14 through 15. FIG. 14 is a rough perspectiveview of a lens barrel including an image shake compensation device and astepping motor having an encoder according to Example 4 of the presentinvention. FIG. 15 is a front view of the lens barrel. The partsdescribed above are indicated by the same reference numerals and theirdescriptions are omitted.

A zooming lens group 45 is held by a zooming lens moving frame 46. Asleeve portion 46 a of the lens moving frame 46 is coupled with a screwmember 52. The screw member 52 is engaged with a lead screw 49 as theoutput axis of a stepping motor 47 having an encoder. Therefore, whenthe stepping motor 47 having an encoder is rotated, the zooming lensmoving frame 46 is moved in the optical axis direction along guide poles32 a and 32 c. A depression 10 a is provided in the fixing frame 10 ofthe shift unit 20 for placing the stepping motor 47 having an encoder ata position such that the stepping motor 47 having an encoder does notoverlap regions where the shift actuators 6 p and 6 y are positioned.

The depression 10 a is provided between the yokes 9 p and 9 y of thepitching and yawing actuators 6 p and 6 y of the shift unit 20. In theshift unit 20, the widths of portions ep and ey of the yokes 9 p and 9 yare larger than portions dp and dy of position detection portions 11 pand 11 y with respect to the center of the optical axis. Effective useof the portions ep and ey is a key factor in the reduction of thedimension of the lens barrel from the center of the optical axis.

The portions dp and dy on the opposite sides are substantially in theshape of a circular arc 10 f as shown in FIG. 15. This allows the shapeof the outer covering of the video camera, which is to be provided atthe outside of the portions, to also be substantially in the shape of acircular arc. Such a video camera having an excellent design can berealized.

The stepping motor 47 having an encoder is provided in such a mannerthat the engaging portion of the screw member 52 of the stepping motor47 having an encoder is positioned at the depression 10 a of the fixingframe 10. Therefore, the stepping motor 47 having an encoder can beprovided at a position close to the optical axis without interferencewith the shift unit 20, thereby making it possible to reduce thediameter of the lens barrel.

As described above, according to Example 4, a depression is provided ina shift lens unit. A stepping motor for zooming is provided in thedepression. Therefore, the lens barrel of Example 4 can have a reducedsize in the radius direction as compared with the conventional lensbarrel, even when the lens barrel of Example 4 is a lens barrel whichincludes an image shake compensation device having two shift actuatorsfor driving the compensation lens group in the optical axis directionand a direction perpendicular thereto.

Although a stepping motor having. an encoder is described as an actuatorfor driving a zoom lens group in the description of Example 4, it isneedless to say that the same effects can be obtained when theconventional stepping motor is used.

Example 5

Next, a fifth embodiment of the present invention will be described withreference to FIGS. 16 through 17. FIG. 16 is a diagram showing a flow ofmagnetic flux leakage of an image shake compensation device according toExample 5 of the present invention. FIG. 17 is a diagram of the lensbarrel shown in FIG. 14 to which a linear actuator is added. The partsdescribed above are indicated by the same reference numerals and theirdescriptions are omitted.

In Example 5, the shift unit 20 and the stepping motor 47 having anencoder are identical to those described in Example 4. Actuators formoving the image compensation lens group 1 are provided along theoptical axis direction and a direction perpendicular thereto. Thestepping motor 47 having an encoder for zooming is provided between theyokes 9 p and 9 y of the pitching and yawing actuators 6 p and 6 y,respectively.

In Example 1, the magnetic sensor 51 is provided at the magnetic centerof the magnetic circuit 38 of the linear actuator 33 so that an externaldisturbance magnetic field of the magnetic sensor 51 for the steppingmotor 47 having an encoder is reduced. However, since the shift unit 20,i.e., the pitching and yawing actuators 6 p and 6 y, are added, magneticflux leakage from the two actuators needs to be reduced. A reductionmethod will be described.

The magnet 8 p of the pitching actuator 6 p is magnetized in such amanner that the upper side thereof has the N pole and the lower sidethereof has the S pole with respect to a direction perpendicular to theoptical axis when viewed from the optical axis object side as shown inFIG. 10. The magnet 8 y of the pitching actuator 6 y is magnetized insuch a manner that the right side thereof has the N pole and the leftside thereof has the S pole with respect to a direction perpendicular tothe optical axis when viewed from the optical axis object side as shownin FIG. 10. In other words, the polarity of the pitching and yawingactuators are opposite to each other. Therefore, in the magnetic circuitincluding a yoke and a magnet, the direction of a magnetic flux flowingin the yoke is opposite to the direction of a magnetic flux flowing inthe yawing, since the polarity of the magnets are opposite to eachother. As a result, the magnetic flux leakage are opposite to eachother.

It is described in Example 1 that the magnetic flux leakage of themagnetic sensor 51 of the stepping motor 47 having an encoder needs tobe reduced with respect to the X and Z directions. Initially, the flowof the magnetic flux leakage will be described. The magnetic fluxleakage of the yawing actuator 6 y flows in a direction indicated byarrow J at the position of the magnetic sensor 51 of the stepping motor47 having an encoder shown in FIG. 16(a). On the other hand, themagnetic flux leakage of the pitching actuator 6 p flows in a directionindicated by arrow k at the position of the magnetic sensor 51 of thestepping motor 47 having an encoder shown in FIG. 16(b).

Therefore, since the directions of the magnetic flux leakage of thepitching and yawing actuators 6 p and 6 y are opposite to each other atthe position of the magnetic sensor 51, the magnetic flux leakagethereof cancels each other, thereby reducing the amount of the magneticflux leakage which enters the magnetic sensor 51. As to the Z direction,there is no influence of the magnetic flux leakage, so that the amountof the magnetic flux leakage which enters the magnetic sensor 51 issmall. Thus, the influence of the magnetic flux leakage can beeliminated with respect to the two directions, i.e., the X and Zdirections, whereby the output of the magnetic sensor is not distortedand therefore a high level of position detection precision can beobtained.

Further, when the stepping motor 47 having an encoder, the linearactuator 33, and the shift unit 20 are provided at the positions of thestepping motor 47 having an encoder, the linear actuator 33 and at thepositions of the shift unit 20 and the linear actuator 33, the influenceof an external disturbance magnetic field is reduced and these can beprovided in a single lens barrel as shown in FIG. 17. Note that thefixing frame 10 is omitted in FIG. 17 for the sake of simplicity.

As described above, according to Example 5, a lens barrel includes ashift unit for performing hand-shake compensation, improving theperformance of the hand-shake compensation. A lens barrel also includesa stepping motor having an encoder, thereby achieving a transportingspeed of about 30-2000 pps. Therefore, hyper-high-speed orhyper-slow-speed zooming can be performed. A high-performance lensbarrel and a video camera using the same can be provided.

Further, when closed loop control is used, the angle of rotation andtorque can be controlled, thereby realizing low power consumption andlow noise. As to a reduction in magnetic flux leakage, a part such as ashield does not need to be used, in contrast to the conventional method,thereby achieving low cost and preventing the size of the lens barrelfrom being increased with an increase in space for parts. A small-sizedand lightweight lens barrel can be provided.

When the stepping motor having an encoder as a magnetic sensor isprovided at the substantial center of the magnetic circuit of the linearactuator as described in Example 4; and the linear actuator is providedat the optical axis imaging plane side of the pitching actuator of theshift unit as described in Example 5, a linear actuator for driving afocusing lens can be incorporated into the lens barrel including theshift unit and the stepping motor having an encoder. Therefore, inaddition to a high-speed response capability, since the magnetic sensoris used, high resolution and a high precision property are obtained,thereby realizing an excellent focusing property.

Needless to say, the same effects can be obtained even if the polarityof the magnets of the pitching and yawing actuators of the shift unitand the magnet of the linear actuator as shown in FIG. 10 is reversed.

Example 6

Next, a sixth embodiment of the present invention will be described withreference to FIGS. 18 through 20. FIG. 18 is a rough perspective view ofa lens barrel including an image shake compensation device, a steppingmotor having an encoder, and an iris unit according to Example 6 of thepresent invention. FIG. 19 is a front view of the lens barrel. FIG. 20is a perspective view of the lens barrel. The parts described above areindicated by the same reference numerals and their descriptions areomitted.

The shift unit 20 of Example 6 is identical to that described in Example2. The pitching moving frame 2 and yawing moving frame 4 of the shiftunit 20 is provided at different heights with respect to the opticalaxis direction, and the yawing moving frame 4 is provided at the opticalaxis imaging plane side. A meter 61 of an iris unit 62 is provided atthe optical axis object side of the yawing moving frame 4. Since themeter 61 of the iris unit 62 is provided in this way, the stepping motor47 for zooming and the shift unit 20 do not interfere with each other.

As described above, a single lens barrel can include the componentsdescribed in Examples 1 through 5, i.e., the five actuators: the shiftunit 20 for compensating image shake, the stepping motor 47 having anencoder, the linear actuator 33, and the iris unit 62 (FIG. 20). Thus, asmall-sized lens barrel having high performance can be achieved.

Example 7

Next, a seventh embodiment of the present invention will be describedwith reference to FIGS. 21 through 22. FIG. 21 is a diagram showing thePSD substrate of a lens barrel according to Example 7 of the presentinvention. FIG. 22 is a diagram showing an arrangement of an LED and aPSD of the lens barrel. The parts described above are indicated by thesame reference numerals and their descriptions are omitted.

The shift unit 20 of Example 7 is identical to that described in Example2. The light emitting elements 12 p and 12 y and the light receivingelements 14 p and 14 y for detecting the positions of the pitching andyawing moving frames 2 and 4 of the shift unit 20 need to be fixed toaccurate positions in order to improve position detection precision. Tothis end, as shown in FIG. 21, the light receiving elements 14 p and 14y are fixed at predetermined positions on the same PSD substrate 15.Further, in order to effectively use a space in the optical axisdirection, the pitching and yawing moving frames 2 and 4 are positionedat different heights. The slits 13 p and 13 y in which the pitching andyawing light emitting elements 12 p and 12 y are provided, respectively,are positioned at the same height.

Accordingly, both in the pitching and yawing moving frames 2 and 4, thegaps between the slits 13 p and 13 y and the light receiving elements 14p and 14y have the same distance c. The amount of light emitted by thelight emitting elements 12 p and 12 y which reach the light receivingsides of the respective light receiving elements 14 p and 14 y are thesame. Therefore, the same position detection precision is achieved bythe light receiving elements 14 p and 14 y.

As described above, in the lens barrel including the shift unit forcompensating hand-shake, the pitching and yawing moving frames arepositioned at different heights with respect to the optical axis.Therefore, the five actuators can be compactly included in the lensbarrel. Further, since the slits of the light emitting elements arepositioned at the same height in spite of the different heights of themoving frames, the two light receiving elements can be provided on thesame substrate. Therefore, the positions of the light receiving elementscan be more precisely determined, thereby improving the positiondetection precision. Furthermore, the substrate carrying the lightreceiving elements can be easily fixed to the fixing frame, therebyimproving ease of assembly.

Example 8

Next, an eighth embodiment of the present invention will be describedwith reference to FIGS. 23 through 24. FIG. 23 is a front view of yawingof an image compensation device of a lens barrel according to Example 8of the present invention. FIG. 24 is a front view of pitching of theimage compensation device. The parts described above are indicated bythe same reference numerals and their descriptions are omitted.

The shift unit 20 of Example 8 is identical to that described in Example2. The flexible print cables 16 and 17, respectively, connecting thepitching and yawing moving frames 2 and 4 with the fixing frame 10 willbe described.

The one end 16 b of the flexible print cable 16 is fixed to the pitchingmoving frame 2 at the side opposite to the pitching actuator 6 p and atthe same side as that of the yawing actuator 6 y with respect to thecenter of the optical axis, being substantially perpendicular to the Zdirection along which the pitching moving frame 2 is smoothly moved. Afirst lens moving frame described in the claims corresponds to such apitching moving frame 2. The one end 17 b of the flexible print cable 17is fixed to the yawing moving frame 4 at the side opposite to thepitching actuator 6 p and at the same side as that of the yawingactuator 6 y with respect to the center of the optical axis, beingsubstantially parallel to the Y direction along which the yawing movingframe 4 is smoothly moved. A second lens moving frame described in theclaims corresponds to such a yawing moving frame 4. The other ends 16 aand 17 a of the respective flexible print cables 16 and 17 are fixed tothe portion 10 e of the fixing frame 10, being substantially parallel tothe Z direction of the pitching moving frame 2.

The image shake compensation device thus constructed will be describedbelow.

The yawing moving frame 4 is driven in the Y direction in the followingway. A current is supplied via the flexible print cable 17 to the coil 7y in response to an instruction from the driving circuit. The flow ofthe current causes the electromagnetic actuator 6 y to generate force inthe Y direction which drives the yawing moving frame 4. The pitchingmoving frame 2 is driven in the Z direction in the following way. Acurrent is supplied via the flexible print cable 16 to the coil 7 p inresponse to an instruction from the driving circuit. The flow of thecurrent causes the electromagnetic actuator 6 p to generate force in theZ direction which drives the pitching moving frame 2. In this case, thepitching and yawing flexible print cables 16 and 17 are bent along an Rportion 10 f provided on the fixing frame 10.

The flexible print cable 16 for pitching is bent at the moving portion16 c between the one end 16 b fixed to the pitching moving frame 2 andthe other end 16 a fixed to the fixing frame 10. Similarly, the flexibleprint cable 17 for yawing is bent at the moving portion 17 c between theone end 17 b fixed to the yawing moving frame 4 and the other end 17 afixed to the fixing frame 10. Therefore, both the flexible print cables16 and 17 can have longer moving portions within such a limited space,so that reaction force is unlikely to be generated in the flexible printcables 16 and 17. This leads to a reduction in load.

As described above, according to Example 8, the moving portions of theflexible print cables of the yawing and pitching moving frames areelongated as much as possible within the limited space. Therefore, aninfluence of reaction force generated by the bending of the flexibleprint cables on the yawing and pitching moving frames can be reduced asmuch as possible. The deterioration of control characteristics can besuppressed. As a result, an image shake compensation device in which thedegree of suppression of image shake is increased can be provided.

Although the other ends of the flexible print cables are fixed to thefixing frame, being substantially parallel to the Z direction, anotherportion of the flexible print cable may be fixed thereto at the fixingposition described herein if the flexible print cables are restricted soas to be substantially parallel to the Z direction.

Example 9

Next, a ninth embodiment of the present invention will be described withreference to FIG. 25. FIG. 25 is a front view of an image compensationdevice of a lens barrel according to Example 9 of the present invention.Note that in FIG. 25 the yawing moving frame 4 is not shown, but onlythe flexible print cable 17 is shown. The parts described above areindicated by the same reference numerals and their descriptions areomitted.

The one end 17 a of the flexible print cable 17 is fixed to the portion10 e of the fixing frame 10, being substantially parallel to the Zdirection. The one end 16 a of the flexible print cable 16 is fixed tothe pitching moving frame 2 at almost the same position as that of theone end 17 a of the flexible print cable 17 of the yawing moving frame4. being substantially parallel to the Z direction along which thepitching moving frame 2 is smoothly moved. The moving portion 16 c ofthe flexible print cable 17 is provided at the outside of the movingportion 17 c of the flexible print cable 17 with respect to the centerof the compensation lens group 1.

The operation of the image shake compensation device thus constructedwill be described below.

The yawing moving frame 4 is driven in the Y direction in the followingway. A current is supplied via the flexible print cable 17 to the coil 7y in response to an instruction from the driving circuit. The flow ofthe current causes the electromagnetic actuator 6 y to generate force inthe Y direction which drives the yawing moving frame 4. The pitchingmoving frame 2 is driven in the Z direction in the following way. Acurrent is supplied via the flexible print cable 16 to the coil 7 p inresponse to an instruction from the driving circuit. The flow of thecurrent causes the electromagnetic actuator 6 p to generate force in theZ direction which drives the pitching moving frame 2. In this case, thepitching moving frame 2 is smoothly moved not only in the Z direction,but in the Y direction in association with movement of the yawing movingframe 4. The fixing portion 10 a of the flexible print cable 16 to thefixing frame 10 is provided at the outside of the optical axis withrespect to the flexible print cable 17 of the yawing moving frame 4.

Therefore, the flexible print cables 16 and 17 are moved as indicated bythe dotted lines, so that the flexible print cables 16 and 17 do notcontact each other.

As described above, according to Example 9, the one ends 16 a and 17 aof the respective flexible print cables 16 and 17 of the pitching andyawing moving frames 2 and 4 are fixed at almost the same position 10 aof the fixing frame 10. The flexible print cable 16 of the pitchingmoving frame 2 is provided on the outside with respect to the opticalaxis. Therefore, the two flexible print cables can be efficientlyprovided within a small space, thereby obtaining the small-sized imageshake compensation device, and the small-sized lens barrel including theimage shake compensation device.

Example 10

Next, a tenth embodiment of the present invention will be described withreference to FIGS. 17 and 25. The parts described above are indicated bythe same reference numerals and their descriptions are omitted.

The one end 17 a of the flexible print cable 17 of the yawing fixingframe 4 is fixed to the fixing frame 10, being substantially parallel tothe Z direction along which the pitching moving device 2 is smoothlymoved. The one end 16 a of the flexible print cable 16 is fixed to thepitching moving frame 2, being substantially parallel to the Z directionalong which the pitching moving device 2 is smoothly moved, similar tothe flexible print cable 17 of the yawing moving frame 4. The flexibleprint cable 16 of the pitching moving frame 2 and the flexible printcable 17 of the yawing moving frame 4 are provided at differentpositions with respect to the optical axis direction. In FIG. 17, theflexible print cable 17 of the yawing moving frame 4 is provided at theoptical axis imaging plate side.

The operation of the image shake compensation device thus constructedwill be described below.

The yawing moving frame 4 is driven in the Y direction in the followingway. A current is supplied via the flexible print cable 17 to the coil 7y in response to an instruction from the driving circuit. The flow ofthe current causes the electromagnetic actuator 6 y to generate force inthe Y direction which drives the yawing moving frame 4. The pitchingmoving frame 2 is driven in the Z direction in the following way. Acurrent is supplied via the flexible print cable 16 to the coil 7 p inresponse to an instruction from the driving circuit. The flow of thecurrent causes the electromagnetic actuator 6 p to generate force in theZ direction which drives the pitching moving frame 2. In this case, themoving portion 17 c of the flexible print cable 17 of the yawing movingframe 4 is bent in the Y direction, and the moving portion 16 c of theflexible print cable 16 of the pitching moving frame 2 is bent in the Zand Y directions. Nevertheless, since the flexible print cables 16 and17 are positioned at different heights with respect to the optical axisdirection, the flexible print cables 16 and 17 do not contact eachother.

As described above, according to Example 10, the flexible print cables16 and 17 of the respective pitching and yawing moving frames 2 and 4are positioned at different heights with respect to the optical axisdirection, so that the two flexible print cables can be efficientlyprovided even within an insufficient space in the plane perpendicular tothe optical axis, thereby obtaining the small-sized image shakecompensation device, and the small-sized lens barrel including the imageshake compensation device.

Example 11

Next, an eleventh embodiment of the present invention will be describedwith reference to FIG. 25. The parts described above are indicated bythe same reference numerals and their descriptions are omitted. The oneend 17 a of the flexible print cable 17 of the yawing fixing frame 4 isfixed to the portion 10 e of the fixing frame 10, being substantiallyparallel to the Z direction along which the pitching moving device 2 issmoothly moved. The moving portion 17 c of the flexible print cable 17is substantially in the shape of a circular arc. The one end 16 a of theflexible print cable 16 is fixed to the pitching moving frame 2 atalmost the same position as the one end 17 a of the flexible print cable17 of the yawing fixing frame 4, being substantially parallel to the Zdirection along which the pitching moving device 2 is smoothly moved.The moving portion 16 c is substantially in the shape of a circular arc.The portion 10 f of the fixing frame 10 opposing to the moving portions16 c and 17 c of the respective flexible print cables 16 and 17 aresubstantially in the shape of a circular arc.

The operation of the image shake compensation device thus constructedwill be described below.

The yawing moving. frame 4 is driven in the Y direction in the followingway. A current is supplied via the flexible print cable 17 to the coil 7y in response to an instruction from the driving circuit. The flow ofthe current causes the electromagnetic actuator 6 y to generate force inthe Y direction which drives the yawing moving frame 4. The pitchingmoving frame 2 is driven in the Z direction in the following way. Acurrent is supplied via the flexible print cable 16 to the coil 7 p inresponse to an instruction from the driving circuit. The flow of thecurrent causes the electromagnetic actuator 6 p to generate force in theZ direction which drives the pitching moving frame 2. In this case, themoving portion 16 c of the flexible print cable 16 of the pitchingmoving frame 2 is positioned at the outside with respect to the movingportion 17 c of the flexible print cable 17 of the yawing moving frame4, and is bent in the Z and Y directions. Nevertheless, since the movingportion 16 c and the corresponding portion 10 f of the fixing frame 10are in the shape of a circular arc, even if the flexible. print cable 16contacts the fixing frame 10, the flexible print cable 16 does not takea large load from the fixing frame 10. Therefore, it is possible tominimize the deterioration of control characteristics due to the load.

As described above, according to Example 11, the moving portions 16 cand 17 c of the respective flexible print cables 16 and 17 and themoving portion 16 a and the corresponding portion 10 f of the fixingframe 10 are in the shape of a circular arc. Therefore, the shape has noprotrusion. In this case, the pitching and yawing moving frames 2 and 4are positioned at different heights with respect to the optical axisdirection, so that the two flexible print cables can be efficientlyprovided even within an insufficient space in the plane perpendicular tothe optical axis, thereby obtaining the small-sized image shakecompensation device. Further, components can be incorporated into anoptical apparatus at high density, so that a small-sized opticalapparatus carrying the lens barrel including the image shakecompensation device can be obtained.

INDUSTRIAL APPLICABILITY

As described above, in the lens barrel of the present invention, anadverse influence of the magnetic flux leakage generated by theactuators can be eliminated.

What is claimed is:
 1. A lens barrel including: a first lens group; asecond lens group; a third lens group; a first actuator for driving thefirst lens group; a second actuator for driving the second lens group;and third and fourth actuators for driving the third lens group, whereinat least one of the first through fourth actuators is provided at aposition such that magnetic flux leakage from at least one of the firstthrough fourth actuators is canceled.
 2. A lens barrel according toclaim 1, wherein the first actuator includes: a stepping motor; a firstmagnet in the shape of a barrel or column, magnetized to have multiplepoles in a circular direction, and attached coaxially to the steppingmotor in such a manner as to rotate; and a first magnetic sensorprovided opposing an outer edge of the first magnet, wherein the secondactuator includes: a second magnet magnetized perpendicular to a drivingdirection; a yoke; a coil provided at a predetermined gap from thesecond magnet, capable of freely moving in the driving direction when acurrent is supplied thereto in such a manner as to flow in a directionperpendicular to magnetic flux generated by the second magnet; and asecond magnetic sensor, and wherein the first magnetic sensor isprovided at a position such that magnetic flux leakage from a magneticcircuit including the second magnet and the yoke is canceled.
 3. A lensbarrel according to claim 1, wherein the second actuator includes: amagnet magnetized perpendicular to a driving direction; a yoke; a coilprovided at a predetermined gap from the magnet, capable of freelymoving in the driving direction when a current is supplied thereto insuch a manner as to flow in a direction perpendicular to flux generatedby the magnet: and a magnetic sensor, wherein the magnetic sensor isprovided at a position such that magnetic flux leakage from at least oneof the third and fourth actuators is canceled.
 4. A lens barrelaccording to claim 1, wherein the third actuator includes a thirdmagnet; the fourth actuator includes a fourth magnet; and the thirdmagnet and the fourth magnet are provided in such a manner that themagnetization of the third and fourth magnets is reversed when viewed inthe center of an optical axis.
 5. A lens barrel according to claim 4,wherein the first actuator includes: a stepping motor; a first magnet inthe shape of a barrel or column, magnetized to have multiple poles in acircular direction, and attached coaxially to the stepping motor in sucha manner as to rotate; and a magnetic sensor provided opposing an outeredge of the first magnet; wherein the third and fourth magnets areprovided at positions such that magnetic flux leakage to the magneticsensor is canceled.
 6. A lens barrel according to claim 1 furtherincluding first and second lens moving frames holding the third lensgroup and capable of being smoothly moved in first and second directionsperpendicular to an optical axis, respectively, wherein one of the thirdor fourth actuators provided at an optical axis imaging plane side isprovided overlapping the lens moving frame provided at an optical axisobject side when viewed in the optical axis direction.
 7. A lens barrelaccording to claim 1, wherein the second actuator is provided at anoptical axis imaging plane side of one of the third and fourth actuatorsprovided at an optical axis object side, overlapping the one of thethird and fourth actuators, when viewed in the optical axis direction.8. A lens barrel according to claim 1 further including first and secondlens moving frames holding the third lens group and capable of beingsmoothly moved in first and second directions perpendicular to theoptical axis, respectively; and a fixing frame holding the first andsecond lens moving frames, leaving the first and second lens movingframes capable of being smoothly moved, wherein the fixing frameincludes a depression in a portion surrounded by the third and fourthactuators; and the first actuator is provided in the depression.
 9. Alens barrel according to claim 1 further including an actuator fordriving an iris, wherein the actuator for driving the iris is providedat the optical axis object side of one of the third and fourth actuatorsprovided at an optical axis imaging plane side.
 10. A lens barrelaccording to claim 1 further including: first and second lens movingframes holding the third lens group, provided at different heights withrespect to an optical axis, and capable of being smoothly moved in firstand second directions perpendicular to the optical axis; a first lightemitting portion incorporated into the first lens moving frame fordetecting a position of the first lens moving frame; and a second lightemitting portion incorporated into the second lens moving frame fordetecting a position of the second lens moving frame, wherein the firstand second light emitting portions are provided at substantially thesame height when viewed in the optical axis direction.
 11. A lens barrelaccording to claim 1 further including: first and second lens movingframes holding the third lends group, and capable of being smoothlymoved in first and second directions perpendicular to an optical axis;and a fixing frame fixing the first and second lens moving frames,leaving the first and second lens moving frames capable of beingsmoothly moved, wherein the third actuator drives the first lens movingframe; the fourth actuator drives the second lens moving frame; the lensbarrel further includes: a first flexible print cable electricallyconnected to the third actuator; and a second flexible print cableelectrically connected to the fourth actuator; wherein one end of thefirst flexible print cable is fixed to the first lens moving frame at aside thereof opposite to the third actuator with respect to the opticalaxis and at the same side as that of the fourth actuator; one end of thesecond flexible print cable is fixed to the second lens moving frame ata side thereof opposite to the third and fourth actuators with respectto the optical axis; and other ends of the first and second flexibleprint cables are fixed to the fixing frame at a side thereof opposite tothe fourth actuator with respect to the optical axis, beingsubstantially parallel to a direction along with the first lens movingframe is smoothly moved.
 12. A lens barrel according to claim 11,wherein the first flexible print cable is provided at an outside fromthe center of the optical axis with respect to the second flexible printcable.
 13. A lens barrel according to claim 11, wherein the first andsecond flexible print cables are provided at different heights withrespect of the optical axis of the third lens group.
 14. A lens barrelaccording to claim 11, wherein moving portions of the first and secondflexible print cables and an outline of the fixing frame correspondingto the moving portions of the first and second flexible print cables aresubstantially in the shape of a circular arc; and the moving portions ofthe first and second flexible print cables can move along the fixingframe.
 15. A lens barrel including: a first lens group; a second lensgroup; a third lends group; a first actuator for driving the first lensgroup; a second actuator for driving the second lens group; third andfourth actuators for driving the third lens group; first and second lensmoving frames holding the third lens group and capable of being smoothlymoved in first and second directions perpendicular to an optical axis;and a fixing frame fixing the first and second lens moving frames,leaving the first and second lens moving frames capable of beingsmoothly moved, wherein the third actuator drives the first lens movingframe, the fourth actuator drives the second lens moving frame, the lensbarrel further includes: a first flexible print cable electricallyconnected to the third actuator; and a second flexible print cableelectrically connected to the fourth actuator; wherein one end of thefirst flexible print cable is fixed to the first lens moving frame at aside thereof opposite to the third actuator with respect to the opticalaxis and at the same side as that of the fourth actuator, one end of thesecond flexible print cable is fixed to the second lens moving frame ata side thereof opposite to the third and fourth actuators with respectto the optical axis, and other ends of the first and second flexibleprint cables are fixed to the fixing frame at a side thereof opposite tothe fourth actuator with respect to the optical axis, beingsubstantially parallel to a direction along which the first lens movingframe is smoothly moved.
 16. A lens barrel according to claim 15,wherein the first flexible print cable is provided at an outside fromthe center of the optical axis with respect to the second flexible printcable.
 17. A lens barrel according to claim 15, wherein the first andsecond flexible print cables are provided at different heights withrespect to the optical axis of the third lens group.
 18. A lens barrelaccording to claim 15, wherein moving portions of the first and secondflexible print cables and an outline of the fixing frame correspondingto the moving portions of the first and second flexible print cables aresubstantially in the shape of a circular arc; and the moving portions ofthe first and second flexible print cables can move along the fixingframe.